Delayed onset of sleep and increased waking times are reported in humans as they transition from childhood into adulthood. In an effort to describe behavioral changes during the adolescent transitional period in nonhuman primates we performed a longitudinal assessment of activity patterns. Sixteen male socially-housed cynomolgus monkeys were fitted with activity collars. Monkeys were maintained in social groups with ad libitum food and water and were maintained on a 12:12 light/dark cycle. Behavioral activity was measured continuously when monkeys were 3 to 7 years of age. Dependent measures included: total activity, activity during the light and dark portions of the light cycle, activity drop-off at the onset of the dark phase, sleep latency, and rise time. Total activity levels decreased with age, while activity during the dark portion of the light cycle increased with age. Sleep latency following lights-off increased between age 3 and age 4, and remained later though age 7. Similarly, rise time after lights-on increased between age 3 and 4, and this increase was maintained to age 7. Activity levels during the light cycle did not change across age group. These data suggest that developmental changes in activity profiles in nonhuman primates are comparable to those reported in human adolescents as they transition to adulthood. Supported by NIH grant AA13995 and P01AA017056-016688.